Note that I use "set ambiwidth=single", since when dealing with Chinese I need to use "set ambiwidth=double".

Could be my version (6.1 i think), or just my tty... but i got errors with the end of the function call: "|set ambiwidth=single", removing this last bit worked fine.

"Create an ftplugin for filetype *.nfo"... uuhm.. like this:

/var/lib/vim/addons/ftdetect/nfo.vim:

au BufNewFile,BufRead *.nfo set filetype=nfo

/var/lib/vim/addons/ftplugin/nfo.vim:

:silent edit ++enc=cp437

/var/lib/vim/addons/ is Debian/Ubuntu system-wide default vim scripts location, could also use /etc/vim/ or ~/.vim/
just create the ftdetect/ftplugin subfolders if they do not exist.
:silent prevents the Press ENTER or type command to continue nag prompt because file gets converted twice and :set cmdheight=2 is not in your vimrc :)